Drying staple fibers



Oct. 22, 1946. H. c. R. FOLMER 2,409,747

DRYING STAPLE FIBERS Filed Jan. 19. 1944 K a a & I

v Q/ A N INVENTOR. waif/{4W ATTORNEY Patented Qct. 22, 1946 DRYING STAPLE FIBERS Herman C. It. Folmer, Swarthmore, Pa., assignor to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application January 19, 1944, Serial No. 518,803

2 Claims. 1

This invention relates to an improved method of drying staple fibers.

Heretofore, stable fibers, after being treated by the usual after-treating processes, have been dried in tunnel dryers. Such drying methods are not entirely satisfactory.

It is known that fibers absorb a certain amount of moisture from the atmosphere under ordinary conditions of exposure thereto. The amount of moisture so absorbed varies, depending upon the particular type of fiber, being, in the case of fibers consisting of regeneratedcellulose, for example, equal to about 7%. It is usual for the manufacturer to supply the textile trade with fibers which retain a residual moisture content equal, or substantially equal, to the amount of moisture which the fibers would normally absorb from the air, so that the fibers will not undergo further change due to moisture absorption.

Mly invention has as its primary object the provision of an economical method of drying staple fibers which permits of the use of high temperatures by means of which all of the staple fibers being treated are rapidly and uniformly dried, and which permits of more precise control of the moisture content of the final products.

My invention contemplates subjecting the moisture laden staple fibers to the action of a hot aeriform current in a closed circulating system, whereby the moisture contained in the fibers is quickly evaporated, separating the dried staple from the moisture abstracted therefrom, and withdrawing the dehydrated staple from the system.

In accordance with the invention, the wet staple, which preferably undergoes a preliminary opening or loosening operation, is suspended in a constantly agitated heated aeriform current for a brief period, and then quickly separated therefrom. The staple fibers are in contact with the air current for such a short time, usually not longer than seconds or so, that it is possible to utilize air heated to very high temperatures, that is temperatures above 200 F., say, of the order of about 200 to 600 F., without impairment of the appearance or properties of the staple, thus greatly facilitating the drying process and materially reducing the time required therefor. Due to the fact that the air current is maintained in a state of more or less constant agitation, all of the fibers suspended therein, and all parts of such fibers, are in constant contact with the hot air, so that all of the fibers are dried at a substan-r tially constant and equal rate, and the danger of 2 overheating some fibers as compared with others, is avoided.

During the drying, the fibers are afforded opportunity to freely shrink and twist, thus assuring a permanent, natural crimp therein, which improves their cohesiveness. Yarns fabricated from such uniformly dried fibers possess uniform non-varying residual shrinkage capacities and strengths throughout their lengths. It is possible, according to the invention, to effectively and uniformly control the residual moisture content. of the fibers so that after drying they retain moisture in an amount substantially equal to the amount of moisture which such fibers normally absorb under conditions of ordinary exposure to the atmosphere.

Since, in the preferred embodiment of the invention, the wet staple fibers, which are preferably fed into the apparatus continuously, at a constant rate of speed, are loosened or opened, and thus separated prior to becoming suspended in the hot aeriform current, the hot air readily and quickly permeates the fibers and rapidly flashes off the moisture from the surface thereof.

' The accompanying drawing represents a simplified elevation illustrating in more or less diagrammatic form suitable apparatus for carrying out the process of the invention.

- process is not to be considered as limited thereto.

Referring to the drawing, the system shown therein includes a heater or furnace l which may be coal, oil, or gas-fired, and to which is'connected a boiler 2 containing a heat transfer material, such as steam or a eutectic mixture of diphenyl and diphenyl oxide for example. An expansion tank 3 is provided to take care of expansion of the heat transfer material during heating thereof. The heat transfer material is circulated by means of circulating pump 4 through conduit 5 teen air heater 6 provided with an air filter I, and in which the heat transfer material gives up its heat to cold air being introduced through inlet 8, after whcih it is recirculatedto boiler 2 through conduit 9.

There are provided two vertically disposed conduits ill and H and, disposed therebetween, a fan It having an inlet port It communicating with the lower end of conduit I0 and an outlet port l5 communicating with the lower end of conduit l I, the upper end of which is connected to a cyclone separator It. It will be evident that the action of fan l2 will draw a current of hot air downwardly from the air heater 6 through vertically 3 disposed conduit l0, and force the same upwardly through conduit l l into the cyclone separator l6. Mounted in the top of the cyclon separator I6 is a fiue or stack IT for permitting the moist air to escape to the atmosphere, thus preventing the apparatus from becoming too humid and impairing the drying efiiciency thereof.

The wet staple fiber in the form of a continuous blanket or mat is continuously fed through squeeze rollers l 8, which remove some of the excess moisture therefrom. The mass of fibers is then carried by conveyor band iii to a blanket disintegrator 20, which breaks up the mat, after which the loosened fibers drop onto the conveyor band 2| and are picked up therefrom by the pins on an endless belt 22, which is shown as a conventional Bramwell feeder, which opens and loosens the wet staple. The opened fibers are removed from thefeeder by the brushing action of wheel 23 which is provided with rubber strips 24, and drop to conveyor band 25, which transports them through rotary seal 26 into conduit I0. The fibers are caught up by and become suspended in the hot air current drawn downwardly through conduit In by fan l2. The current of hot air carrying the fibers in suspension therein is forced upwardly by the action of fan [2 through conduit II and enters the cyclone separator IS on a tangent with the circumference thereof, and is thereby made to take a circuitous path in the separator, the fibers being thrown outwardly against the body walls of the separator, through centrifugal force, from which they drop by gravity through vertically disposed conduit 21 onto conveyor band 28. The fibers may be sulficiently opened at this point and if so, they may be directed to a baling press bin and thence to a baling press, or they may be subjected to an-additional opening operation in which case they are carried by conveyor band 28 through rotary seal 29 to an opener 30 in which they are again subjected to loosening or opening which, in this in; stance, is efiected while the staples are in the dry state. .A fan- 3| is provided which, through suction, draws the fibers from the dry opener upwardly through conduit 32 into separator 33, in which the fibers are separated from the carrier air. From separator 33, the fibers are discharged into a baling press bin 34, and then to a baling press 36. A filter bag 36 is provided to receive any fibers which adhere to separator 33 and which are withdrawn therefrom by the action of fan 3|.

In the cyclone separator Hi, the fibers are separated from the drying air containing the moisture abstracted therefrom. A damper 31 i pivotally mounted in fine or stack IT. The damper 31 is so adjusted that only-a predetermined portion of the moist air escapes through flu I! to the atmosphere, the remainder thereof being returned through conduit 38 to air heater 6, where it mingles and becomes admixed with cold air introduced to the heater through inlet 3. By proper adjustment of the amount of moistureladen air returned to air heater 6, and control of the amount of cold air introduced through inlet 3, it is possible to constantly control the temperature of the air being circulated through the system, which insures a uniform temperature and thus a uniform rate of drying of the fibers.

The apparatus illustrated comprises a single drying unit, but several such units may be combined to provide a multi-unit drying system, in which all of the air heaters of the individual units are supplied by a heat transfer material circulated thereto from a single boiler connected to a single centrally located furnace.

My improved method of drying results in staple fibers of superior quality and improved tensile strengths. The process also has the advantage that it may be carried out by means of apparatus which may be operated for indefinite periods of time, the wet staple being continuously supplied thereto, and uniformly dried staple being continuously withdrawn therefrom. Due to the rapid circulation of the aeriform current in which the fibers are suspended there is no tendency for the fibers to adhere to the walls of the apparatus, and frequent servicing thereof to relieve clogging is unnecessary. The apparatus which may be employed requires a relatively small capital outlay and does not require an excessive amount of floor space.

Staple fibers of any artificial or natural origin may be dried accordin to my improved process, such as staple obtained by cutting continuous filaments consisting of regenerated cellulose from viscose or cuprammonium cellulose; cellulose derivatives such as cellulose esters, particularly cellulose acetate; mixed cellulose esters; cellulose ethers, as for example, ethyl cellulose; glass; mineral wool filaments; resinous materials such as acrylate resins; polyvinyl resins such as polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, after-chlorinated polyvinyl chlo-.

ride, and after-chlorinated copolymers of vinyl chloride and vinyl acetate; nylon; proteinaceous materials such as casein; natural silk, etc.

I claim:

1. Method of handling moisture-laden artificial fibers which comprises subjecting the fibers in the form of a web to a disintegrating opera- ,tion to loosen the fibers, opening the loosened fibers, continuously projecting the opened fibers into a current of hot air, throwing the fibers suspended in the air current upwardly along an unimpeded substantially vertical path to dry the fibers while permitting uniform free shrinkage thereof, continuously separating the dried fibers from the air after they have been in contact therewith for a period of time not longer than about five seconds. and collecting all of the separated fibers to prevent commingling thereof with moisture-laden fibers.

2. Method of handling moisture-laden arti ficial staple fibers which comprises subjecting the fibers in the form of a web to a disintegrating operation. to loosen the fibers, opening the loosened fibers, continuously projecting the opened fibers into a current of hot air, throwing the fibers e suspended in the air current upwardly along an unimpeded substantially vertical pathto dry the fibers while permitting uniform free shrinkage thereof, continuously separating'all of the dried fibers from the air after they have been in contact therewith for a period of time not longer than about five seconds, collecting all of the separated fibers to prevent commingling thereof with moisture-laden fibers, and subjecting the separated fibers to further opening.

- HERMAN C. R. FOLMER. 

